1. Field of the Invention
The present disclosure relates to a dual holography three dimensional display device. Especially, the present disclosure relates to a non-glasses type 3D display device in which the holography 3D images are divided into the left-eye 3D images and the right-eye 3D images for representing the real 3D images.
2. Discussion of the Related Art
Recently, many technologies and researches for making and reproducing the 3D (Three Dimensional) image/video are actively developed. As the media relating to the 3D image/video is a new concept media for virtual reality, it can improve the visual information better, and it will lead the next generation display devices. The conventional 2D image system merely suggests the image and video data projected to plan view, but the 3D image system can provide the full real image data to the viewer. So, the 3D image/video technologies are the True North image/video technologies.
Typically there are three methods for reproducing 3D image/video; the stereoscopy method, the holography method and the integral imaging method. Among them, the holography method uses laser beam so that it is possible to observe the 3D image/video with naked eyes. The holography method is the most ideal method because it has an excellent visual autostereoscopic property without any fatigue of observer.
To produce a recording of the phase of the light wave at each point in an image, holography uses a reference beam which is combined with the light from the scene or object (the object beam). If these two beams are coherent, optical interference between the reference beam and the object beam, due to the superposition of the light waves, produces a series of intensity fringes that can be recorded on standard photographic film. These fringes form a type of diffraction grating on the film, which is called the hologram. The central goal of holography is that when the recorded grating is later illuminated by a substitute reference beam, the original object beam is reconstructed (or reproduced), producing a 3D image/video.
There was a new development of the computer generated holography (or CGH) that is the method of digitally generating holographic interference patterns. A holographic image can be generated e.g. by digitally computing a holographic interference pattern and printing it onto a mask or film for subsequent illumination by suitable coherent light source. the holographic image can be brought to life by a holographic 3D display, bypassing the need of having to fabricate a “hardcopy” of the holographic interference pattern each time.
Computer generated holograms have the advantage that the objects which one wants to show do not have to possess any physical reality at all. If holographic data of existing objects is generated optically, but digitally recorded and processed, and brought to display subsequently, this is termed CGH as well. For example, a holographic interference pattern is generated by a computer system and it is sent to a spatial light modulator such as LCSML (Liquid Crystal Spatial Light Modulator), then the 3D image/video corresponding to the holographic interference pattern is reconstructed/reproduced by radiating a reference beam to the spatial light modulator. FIG. 1 is the structural drawing illustrating the digital holography image/video display device using the computer generated holography according to the related art.
Referring to FIG. 1, the computer 10 generates a holographic interference pattern of an image/video data to be displayed. The generated holographic interference pattern is sent to a SLM 20. The SLM 20, as a transmittive liquid crystal display device, can represent the holographic interference pattern. At one side of the SLM 20, a laser source 30 for generating a reference beam is located. In order to radiate the reference beam 90 from the laser source 30 onto the whole surface of the SLM 20, an expander 40 and a lens system 50 can be disposed, sequentially. The reference beam 90 out from the laser source 30 is radiated to one side of the SLM 20 passing through the expander 40 and the lens system 50. As the SLM 20 is a transmittive liquid crystal display device, a 3D image/video corresponding to the holography interference pattern will be reconstructed/reproduced at the other side of the SLM 20.
The holography type 3D display system according to the FIG. 1 comprises a light source 30 for generating the reference light 90, an expander 40 and a lens system 50 which have relatively large volume. In case that this kind 3D display system is configured, it may have large volume and huge weight. That is, the conventional arts for the holography type 3D display system are not adequate to apply to the thin, light and portable display systems which are recently required. Therefore, it is required to develop a thin flat type holography 3D display system which can represent the real 3D images with the naked eyes.